Promised green revolution still seems a long way off

Climate change will have a profound impact on agriculture in the coming decades, either directly or indirectly.

An increase in extreme weather will lead to poor harvests - a trend that has already started - and demand for biofuel will take land away from food production. Other factors such as urbanisation and increased demand for meat and dairy products in developing countries will also increase demands for food.

"The pressures on the land and on agriculture are now much higher than we have ever seen," said Dr Les Firbank at the publicly funded Institute of Grassland and Environmental Research at North Wyke, Devon. He led the government's independent scientific assessment of the impact of GM crops on the environment, the so-called farm-scale evaluations, which ended in 2005.

But he said people were also aware of the other services provided by agricultural land such as flood protection and clean water. "It's not like the time at the end of the second world war where we wanted to ramp up food production at any cost. We are trying to ramp up production, ramp up environmental quality. We are also trying to ramp up the social benefits of the land," Firbank said.

Proponents of GM food argue that the technology could create a "green revolution" that would help farmers grow food more productively and in places that have not been cultivated before, such as regions prone to drought.

"You hear a lot of hype from the industry about the benefits that GM crops will bring, but despite 30 years of research and 10 years of commercialisation we are still nowhere nearer to tackling these challenges than we were at the beginning," said Claire Oxborrow of Friends of the Earth. "The industry has not managed to bring a single product to the market that is able to tackle these issues."

The GM crop varieties on the market fall broadly into two categories: insect resistance and herbicide tolerance. But it is wrong to say there has not been progress in other areas, said Professor Chris Leaver, a plant scientist at Oxford University.

He said the firms Monsanto and Syngenta are both field trialling experimental salt-tolerant crops, for example. "They are looking good, but they are not commercialisable yet," said Leaver.

Salt and drought tolerance are more complex traits than herbicide and insect tolerance, which rely on a single gene. "Plants have evolved a number of traits to address [salt and drought tolerance]. This is not just single genes, there are probably several genes," Leaver said.

So engineering drought and salt tolerance is a more difficult scientific challenge.

"We need all the tools we can get and GM provides some of those tools," Firbank said. "As long as those tools are used safely and there are appropriate levels of safeguards then as far as I'm concerned, why not?" But he said it was simplistic to present GM as a panacea.

Other solutions such as changing farming systems should all be pursued. "It's a case by case issue. It's not about some sort of blanket, yes this is great or no this is awful," he added.

What is clear is that GM agriculture is increasing. According to a report from the International Service for the Acquisition of Agri-biotech Applications, a not-for-profit organisation, the area of agricultural land under GM crop cultivation worldwide increased by 12% in 2007 to 114m hectares (258m acres). Worldwide use has increased 70-fold in the last decade.